This invention relates generally to inflators for use in inflating inflatable restraint airbag cushions, such as used to provide impact protection to occupants of motor vehicles. More particularly, the invention relates to inflator devices having multiple or plural stages or levels of inflation gas output and as such may be used to provide an inflation gas output which is adaptive to factors such as one or more crash and occupant conditions.
It is well known to protect a vehicle occupant by means of safety restraint systems which self-actuate from an undeployed to a deployed state without the need for intervention by the operator, i.e., “passive restraint systems.” Such systems commonly contain or include an inflatable vehicle occupant restraint or element, such as in the form of a cushion or bag, commonly referred to as an “airbag cushion.” In practice, such airbag cushions are typically designed to inflate or expand with gas when the vehicle encounters a sudden deceleration, such as in the event of a collision. Such airbag cushions may desirably deploy into one or more locations within the vehicle between the occupant and certain parts of the vehicle interior, such as the doors, steering wheel, instrument panel or the like, to prevent or avoid the occupant from forcibly striking such parts of the vehicle interior. For example, typical or customary vehicular airbag cushion installation locations have included in the steering wheel, in the dashboard on the passenger side of a car, along the roof line of a vehicle such as above a vehicle door, and in the vehicle seat such as in the case of a seat-mounted airbag cushion. Other airbag cushions such as in the form of knee bolsters and overhead airbags also operate to protect other or particular various parts of the body from collision.
In addition to an airbag cushion, inflatable passive restraint system installations also typically include a gas generator, also commonly referred to as an “inflator.” Upon actuation, such an inflator device desirably serves to provide an inflation fluid, typically in the form of a gas, used to inflate an associated airbag cushion. Various types or forms of inflator devices have been disclosed in the art for use in inflating an inflatable restraint system airbag cushion. One particularly common type or form of inflator device used in inflatable passive restraint systems is commonly referred to as a pyrotechnic inflator. In such inflator devices, gas used in the inflation of an associated inflatable element is derived from the combustion of a pyrotechnic gas generating material.
In view of possibly varying operating conditions and, in turn, possibly varying desired performance characteristics, there is a need and a desire to provide what has been termed an “adaptive” inflator device and a corresponding inflatable restraint system. With an adaptive inflator device, output parameters such as one or more of the quantity, supply, and rate of supply of inflation gas, for example, can be selectively and appropriately varied dependent on selected operating conditions such as one or more of ambient temperature, occupant presence, seat belt usage and rate of deceleration of the motor vehicle, for example.
Pyrotechnic inflators typically may have one or more chambers containing gas generant. Adaptive pyrotechnic inflators having gas generant material in two chambers, for which reaction is each independently initiated by a specified initiator, have been referred to as “dual stage” inflators.
In practice, each such gas generant material-containing chamber is oftentimes referred to as a “combustion chamber” as the gas generant material therein contained is burned or otherwise reacted to produce or form gas such as may be used to inflate an associated inflatable restraint airbag cushion. The initiators are typically electrically-actuated. As a result, dual stage tubular passenger inflators are commonly configured with one initiator electrical connection on each of two opposite ends of a tubular-shaped inflator body. Such an inflator construction necessitates an inflatable restraint system airbag module that allows access to both ends of the tubular inflator so that appropriate required electrical connections can be made thereto.
Dual stage inflators may have several contemplated firing scenarios. In a first such scenario, only the gas generant material in a first or primary chamber is actuated whereby a fixed quantity of inflation gas is produced thereby. In a second possible firing scenario, the first or primary chamber is first actuated whereby gas generant material in the first chamber is first reacted to start to produce or form inflation gas and after a predetermined or preselected delay, the gas generant material in a second or secondary chamber is then actuated whereby gas generant material in the second chamber is reacted to also produce or form inflation gas. In a third possible firing scenario, the gas generant material in the first chamber and the gas generant material in the second chamber are actuated simultaneously to produce or form inflation gas from the gas generant material in each of the chambers.
As will be appreciated, through the selection and use of an appropriate such firing scenario, inflator output parameters such as one or more of the quantity, supply, and rate of supply of inflation gas, for example, can be selectively and appropriately varied dependent on selected operating conditions such as one or more of ambient temperature, occupant presence, seat belt usage and rate of deceleration of the motor vehicle, for example.
Multi-stage and adaptive inflator devices find widespread use in modern day vehicle occupant safety restraint systems. Such use leads to a need and desire for improved such inflator devices such as capable of specifically varying selected inflation performance scenarios. Thus, there is a need and demand for such inflator devices and associated methods of operation of increased simplicity and reliability of operation and design. In particular, there is a need and demand for such inflator devices and associated methods of operation that provide or result in specifically desired inflation performance scenarios in a less costly and/or more efficient manner.